Carbon nanotubes may be applied in various fields as a material for the vehicle industry, electronic industry, defense industry, energy industry, and environmental industry due to excellent mechanical strength, thermal conductivity, electric conductivity, and chemical stability thereof. In 1991, Dr. Iijima of NEC found a thin and long tube-shaped carbon nanotube in the procedure where a carbon formed on a graphite negative electrode by using an electrical discharge method was analyzed through a transmission electron microscope (TEM), which was first published in the Journal of Nature, and this was the beginning of carbon nanotube. The carbon nanotube is that a graphite surface is rolled in a nano-sized diameter, and exhibits metal or semiconductor characteristics depending on the rolling angle and structure of the graphite surface. The carbon nanotube is anticipated to be applied as an ultrafine connection line, an ultrafine pipe, an ultrafine liquid injection apparatus, a gas sensor, and a medical material using affinity with biological tissues. An application of the carbon nanotubes that shields and absorbs electromagnetic waves is one of the fields that have actively been studied in recent. In addition, the application of carbon nanotubes is actively studied as a material for a solar cell or a fuel battery, which is spotlighted as an alternative energy source, and a material for vehicle components requiring a small weight and a high strength.
However, a carbon nanotube-metal composites and metal oxide composites have higher performances than the carbon nanotube itself, for electronic industry materials, such as an electrode material for a field emission type flat panel display, a fuel cell, and a solar cell, a hydrogen storage material for a fuel cell, an electromagnetic wave shielding and absorbing material, an electronic ink source material, and the like; and high-strength materials, such as high-strength light-weight tool steel, high-strength light-weight vehicle parts, and defense industry materials. This is a new material obtained by inducing a functional group to the carbon nanotube and allowing the induced functional group to react with metal (iron, tin, aluminum, titanium, or the like) to thereby chemically combine them. Due to the metal component contained therein, this has superior characteristics in molding structure bodies, such as, manufacturing a field emission display, manufacturing a hydrogen storage device combined body, manufacturing an electrode, manufacturing a super capacitor, manufacturing an electromagnetic shielding and absorbing body, manufacturing a small-weight and high-strength application product, and the like. Particularly, the carbon nanotube-metal and carbon nanotube-metal oxide may be used for manufacturing the electromagnetic shielding and absorbing body. Currently, silver, iron oxide, and the like are used for manufacturing the electromagnetic shielding and absorbing body. Particularly, ferrite, carbonyl iron, or the like may be used as the iron oxide in the electromagnetic absorbing body, and thus, the development of a material that can substitute for them is requested. The ferrite as the iron oxide has less magnetism than iron itself, but, currently, has been widely used due to long-term material stability thereof.
The carbon nanotube-metal and carbon nanotube-metal oxide have different metal properties from the existing metals in the case where the metal and the metal oxide particles combined therein have a nano-level size. The representative physical property change is that the melting point of metal becomes reduced. In addition, the smaller the size of the metal nanoparticle combined, the lower the melting point. This change makes the carbon nanotube-metal composites and metal oxide composites have different physical properties from the existing materials, resulting in new material characteristics, thereby allowing various applicability.
Korean Patent Nos. 10-616071 and 10-778094 disclose a method of reducing a metal precursor by inputting the metal precursor and a reducing agent in a carbon nanotube-dispersed solvent. However, in the above patents, a reducing reaction due to the input of the reducing agent is not uniform in the entire reaction liquid, and thus, the particle size is not uniform and the dispersibility is degraded.